The present invention relates to a pneumatic float for light and ultra-light aircraft in accordance with the preamble to claim 1.
Several such pneumatic floats, that is inflated with compressed air, are known. The closest to the present invention, representing the state of the technology, are for instance published in U.S. Pat. No. 4,697,762 (D1), U.S. Pat. No. 2,391,326 (D2), U.S. Pat. No. 2,522,340 (D3) and U.S. Pat. No. 2,345,143 (D4). Whilst in D2, D3, and D4 the general state of the technology is limited, D1 lies closest to the present invention. A float is published in D1, which comprises a flexible outer hull of strong woven fabric, which is constructed from an upper side, a lower side and side walls. The upper and lower sides are joined by a number of similarly textile webs built in essentially vertically and along the main direction of the float. At a position somewhat to the rear of the centre the float has a step, which was published in DE 600 321 as early as 1933 and has been applied and further developed since then.
In the cross section through the float in D1 at the position of this quoted step, similarly an essentially vertical web is built in, however perpendicular to the main direction of the float. In the chambers, which are formed between the webs and between the webs and the side walls, airtight bladders are inserted, which are inflated with compressed air and provide the float on the one hand with the necessary buoyancy and on the other hand a certain stability.
To increase the stability and rigidity, stiffening elements are built into the region in front of the step mentioned, which are provided partly of rigid foam, partly of plywood. A shoe is fastened on the outside of the fabric-constructed float, which additionally stiffens the underside of the forward part and is to protect the float from damage. This shoe is made, for instance from plastics material.
The introduction of force from the undercarriage of the aircraft onto the two floats constructed as described occurs via two spars running longitudinally over the entire length of each float. These lie to the side on top of the floats and are lashed and fastened by long lashings. The total of four spars are joined by two transverse spars on which the aircraft is supported, whereby the rear transverse spar lies somewhat in the position where the underside of the float has the step mentioned.
If one takes the intended area of application of the float according to D1 into account, then the major advantage claimed is weight conservation. Since the selected method of construction of the purely pneumatic part of the float has, however, insufficient stiffness, all sorts of measures have to be provided for its increase, which are not pneumatic, and therefore heavier, in part indeed substantially heavier, than air or purely pneumatic components. Furthermore at the height of the step the longitudinal webs are interrupted by the transverse web. Owing to the introduction of force at the rear transverse spar also lying at about this point there results in this region a joint-like weakening of the float in one of the constructions claimed in D1 which has to be strengthened and tensioned by a compression leg passing vertically through the float and two wire ropes.
It is also not obvious from D1, how other cross section formsxe2x80x94for instance such as those with a V-shaped bottom partxe2x80x94can be constructed in accordance with the invention. From the chosen construction it can be at least anticipated that, in addition to the disadvantages mentioned, the float according to D1 also cannot be economically manufactured.
It is therefore the aim of the present invention to produce pneumatic floats for light and ultra-light aircraft, which overcome the stated disadvantages, which are light and rigid and can also be manufactured cost-effectively.